The AIR-BX2 study enrolled people with non-cystic fibrosis (non-CF) bronchiectasis and gram-negative airway infection. Participants received two 28-day courses of either Aztreonam for Inhalation Solution (AZLI) or placebo taken 3 times a day. Each course was followed by a 28-day off-drug period. Following the two blinded courses, all participants received a 28-day course of open-label AZLI then were followed for an additional 56 days.